Fracturing Fluid Filtration System for Minimizing Production Screen Clogging

ABSTRACT

Treatment fluid is screened at a surface location to the same particle size that the mud is screened before delivery into treating equipment in the borehole. Solids or microgels that can form are captured before pumping into the borehole to prevent fouling of screens designed to keep formation solids out of the produced fluids to the surface.

FIELD OF THE INVENTION

The field of the invention is methods of addressing fouling of screenedopenings in fracturing systems by screening fluids before pumping into afracturing assembly.

BACKGROUND OF THE INVENTION

Typically pressures in the borehole are controlled with mud systems. Themud is treated at the surface when returning from the borehole withvibrating screens, cyclone separators and other filtration equipmentbefore being pumped back into the borehole. The circulating mud canremove cuttings from milling operations, solids entering the mud fromsloughing off from the borehole wall or many other circumstances. Thefiltration devices target a predetermined mesh size.

Fracturing can be accomplished in a variety of ways but one way is touse a series of two position sleeve valves actuated sequentially withprogressively larger balls landed on seats of each sleeve. The sleeve isin an open position for fracturing and then is shifted to a screenedposition for subsequent screening of later production flow. The screenedposition of one sliding sleeve is used to flow through to deliver abigger ball with flow through the open screened position. The flow thatdelivers the progressively larger balls to accomplish the treatment is aspecial formulation that can create solids or gels of a size largeenough to create a clogging situation when trying to deliver the nextball with flow out through an open screened port. This could slow theprocess by lengthening the time to get the ball to the seat or it mayfoul the screened opening to such a degree that subsequent productioninto the string through the screened opening can be prevented. Thepresent invention responds to this situation with a filtration systemfor the treatment fluid before being delivered downhole down to the sameor smaller particle size that the particles in the mud are screened out.These and other aspects of the present invention will be more readilyapparent to those skilled in the art from a review of the detaileddescription of the preferred embodiment and the associated drawing whilerecognizing that the full scope of the invention is to be determined bythe appended claims.

SUMMARY OF THE INVENTION

Treatment fluid is screened at a surface location to the same particlesize that the mud is screened before delivery into treating equipment inthe borehole. Solids or microgels that can form are captured beforepumping into the borehole to prevent fouling of screens designed to keepformation solids out of the produced fluids to the surface.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 schematically illustrates the filtration of treating fluid at asurface location before pumping into the borehole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

During well construction operations such as drilling, fracturing, and/orcompletion operations fluids are used which contain solids forweighting, such as drilling muds. Another example of fluids used aretreating fluids such as polymer viscosifiers used to transport proppantor improve acid placement during reservoir stimulation.

There are instances where screens or filters at added in the well toprevent the proppant or formation sand from flowing back out of the wellduring production. These screens or filters can be run into the wellduring drilling or after drilling is completed. The screens or filtershave a known range of opening sizes desired to prevent the flow ofcertain sand or proppant sizes during production operations of thereservoir.

Typically drilling mud is conditioned through a surface screening systemof hydrocyclones and surface shaker screens to condition the mud to aparticle size range that will not plug the screens or filters that areplaced in the wellbore.

However, during stimulation operations such as fracturing or acidizingthe fluids polymer viscosifiers are used which may be mixed in filteredfluids but once viscosified contain particles or microgels that yieldlarger particle sizes than are acceptable to prevent plugging of thescreens or filters placed in the wellbore.

The present invention relates using a screen to ensure the particle sizeof any solids or microgels in the stimulation treating fluids arescreened to the same particle sizes or less than the particle sizesachieved during screening of the drilling mud.

In the schematic diagram box 10 represents the mud mixing equipment thatis then pumped with pumping equipment 12 and filtered to a predeterminedparticle size in filtration system 14. Some filtration can also takeplace with returning mud flow to the surface. The point being that thesolids size that remains in the mud is smaller than a predetermined sizeto avoid screen fouling or clogging up small clearance spaces in theborehole.

Treatment fluids are mixed in blending system 16 and pumped by pumpingsystem 18 and filtered in filtering system 20 to separate solids to thesame or greater extent than in filtration system 14. It is the additionof the filtration system 20 that prevents clogging of screened openings22 as will be described below.

Typically when treating with a series of sliding sleeves operated with aseated ball on a seat there are multiple positions for the slidingsleeve assembly 24. As illustrated, the screened opening 22 is alignedwith opening to screen out solids from production after treatingschematically represented by arrow 28. Prior to that the treatmenthappens when ports 30 are aligned with opening 26. Pressure on a seatedball on sleeve 24 shifts it to align screened opening 22 with opening26. The ball that shifts the sleeve is blown through and the next ballfor another sleeve uphole is pumped into the borehole using the screenedopening 22 aligned to opening 26 as the path for pumping so that thenext ball in sequence can be delivered with pumped treatment fluid. Inthe past pressure buildup on the inside of screened opening 22 has beennoticed by surface personnel by virtue of an increase in surfacepressure on the positive displacement pumps at the surface to move thedesired fixed volume rate when delivering the next ball. The reason forthis has been that solids formed in the treatment fluid mixture whenintroduced to the borehole have not been screened either at all or tothe degree where they can pass through the screened opening 22.Deposition of such solids on the tubing side of screened openings 22 canembed in the screen and not only impede the treatment process byextending the time to deliver balls to seats but can also slow ultimateproduction flows when the well is put onto production.

The present invention addresses this by filtration of treating fluidsbefore introduction into the borehole to the same or greater degree thanthe filtration systems currently incorporated into mud circulatingsystems.

The teachings of the present disclosure may be used in a variety of welloperations. These operations may involve using one or more treatmentagents to treat a formation, the fluids resident in a formation, awellbore, and/or equipment in the wellbore, such as production tubing.The treatment agents may be in the form of liquids, gases, solids,semi-solids, and mixtures thereof. Illustrative treatment agentsinclude, but are not limited to, fracturing fluids, acids, steam, water,brine, anti-corrosion agents, cement, permeability modifiers, drillingmuds, emulsifiers, demulsifiers, tracers, flow improvers etc.Illustrative well operations include, but are not limited to, hydraulicfracturing, stimulation, tracer injection, cleaning, acidizing, steaminjection, water flooding, cementing, etc.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below:

I claim:
 1. A borehole treatment method, comprising: pumping treatmentfluid through at least one tubular wall opening at a first location;positioning a screen in said at least one wall opening at a firstlocation after said pumping; opening a second at least one wall openingin the tubular wall with pumped treatment fluid filtered to removeparticles larger than openings in the screen at the first location. 2.The method of claim 1, wherein: landing objects on respective at leastone first and second sleeves at said first and second locations to opensaid at least one wall openings at said first and second locations. 3.The method of claim 2, wherein: shifting a screen into position at saidtubular at least one wall opening at said first location with movementof a said at least one first sleeve after treatment through said atleast one wall opening without the screen aligned with said at least oneopening at said first location.
 4. The method of claim 3, wherein:pumping one of said objects to said second sleeve as flow passes throughsaid first screen at said first location.
 5. The method of claim 4,wherein: shifting said at least one second sleeve with one of saidobjects landed on said at least one second sleeve to open the at leastone tubular wall opening at said second location.
 6. The method of claim5, wherein: isolating the at least one screened wall opening at saidfirst location when shifting said at least one second sleeve to opensaid at least one tubular wall port at said second location.
 7. Themethod of claim 1, wherein: blending filtered treatment fluid at asurface location with filtered drilling fluid before pumping into theborehole.
 8. The method of claim 1, wherein: filtering out solids ormicrogels from the treatment fluid.
 9. The method of claim 1, wherein:filtering drilling fluid to the same particle size as solids ormicrogels in the treatment fluid.
 10. The method of claim 9, wherein:blending filtered treatment fluid at a surface location with filtereddrilling fluid before pumping into the borehole.
 11. The method of claim1, wherein: using the same wall opening at the first location without ascreen before moving the screen into said same wall opening.
 12. Themethod of claim 1, wherein: using different wall openings as said atleast one wall opening at said first location; opening a first of saidopenings without a screen at said first location for said pumping beforeopening a second said wall opening at said first location, said secondwall opening at said first location being screened when opened.
 13. Themethod of claim 12, wherein: closing said screened opening without ascreen and opening the second wall opening that is screened when openedat said first location when opening said at least one opening at saidsecond location.